linux-kernel - Re: bug fix for registers debugfs file implementation [RFC]

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Message-ID: <20170424120451.dw5nhdpockesrg3n@sirena.org.uk>
Date:   Mon, 24 Apr 2017 13:04:51 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
Cc:     Variksla <variksla@...il.com>, linux-kernel@...r.kernel.org,
        gregkh@...uxfoundation.org
Subject: Re: bug fix for registers debugfs file implementation [RFC]

On Mon, Apr 24, 2017 at 10:02:31AM +0100, Charles Keepax wrote:
> On Sat, Apr 22, 2017 at 01:28:15PM -0700, Variksla wrote:
> > > On Apr 21, 2017, at 10:27 AM, Mark Brown <broonie@...nel.org> wrote:

> > > If I remember correctly this is done the way it is because seq_file has
> > > to iterate through the entire file to get to the point being read by the
> > > application.  This is a *very* big overhead for some applications (like
> > > monitoring some registers to see what they're doing) on bigger devices,

> > Wondering why would the user space application be monitoring the registers?

> We do have tooling that accesses and occasionally monitors
> registers using the debugfs files. It is often used by hardware
> types while testing/debugging issues. And as Mark points out

Even without an actual program explicitly written for it interactive
monitoring of the register map can be done by a person as well which is
just as much of an application (and the major point of the file).

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